Former major-leaguer Ryan Freel’s parents have donated his brain to the Boston University Center for the Study of Traumatic Encephalopathy to search for evidence of injuries that might have led to his suicide earlier this month, The New York Times reported.

Freel, 36, was found dead Dec. 22 in his Jacksonville home. Authorities there concluded that he had died of a self-inflicted shotgun wound.

Ryan Freel played in more than 500 MLB games from 2001 to 2009. (AP Photo)

According to The Times, an accumulation of concussions, as well as mood swings and troubling incidents, left relatives—and Freel himself—apprehensive about his well-being.

Based on recollections by Freel’s mother and his own statements, his stepfather, Clark Vargas, estimated to The Times that Freel may have sustained 15 concussions, 10 in baseball, a sport not typically associated with head trauma.

“He was a hard driver,” Vargas told The Times. “It was not a career to him. It was a game that he played hard.”

Boston University is leading the research into the possible correlation between concussions in athletes and a degenerative brain disease known as chronic traumatic encephalopathy.

The research was prompted by a rash of suicides and cases of dementia, primarily among retired NFL players.

Freel’s parents approved the donation of tissue to search for evidence of CTE, which might in part explain his decline.

An eight-year major-league veteran, Freel’s last head injury may have been in 2009, his final season, when he was struck by a pickoff throw. He was placed on the disabled list and finished his playing days in the minor leagues.

Freel had consulted with doctors and undergone examinations, mostly psychological, and even became aware of the CTE studies, his ex-wife, Christie Moore Freel, told The Times.

She acknowledged, however, that the head injuries might not fully explain why her former husband took his life. “Ryan had a lot of battles, fought a lot of demons,” said Christie Moore Freel, who was divorced from Freel in April after 11 years of marriage.

Freel was arrested at least once for drunken driving and on another occasion for disorderly intoxication.